The present invention relates to a body implantable treatment device intended for fixation in body lumens such as the esophagus, bile duct and blood vessels.
There are many situations requiring interventional procedures to repair damage to a body vessel. For example, carcinomas in the esophagus and the bile duct can lead to progressive closing of the lumen. A fistula in the trachea and esophagus can render those vessels inoperable. Similarly, an aneurysm in a blood vessel may rupture and render the blood vessel useless for maintaining blood flow therethrough. One means of repairing such a body vessel is by implanting a stent in the area of the damage. A radially self-expanding stent such as described in U.S. Pat. Nos. 4,655,771 and 5,061,275 is preferred because its radially self-expanding characteristics facilitate delivery of the stent to the treatment site. Such a stent can be constrained at a diameter smaller than its diameter in an unconstrained state and placed on a suitable delivery device. The delivery device in turn can be placed in the body percutaneously so the constrained stent is located adjacent the treatment site. When the means constraining the stent on the delivery device is removed, the stent radially self-expands into place.
However, such a self-expanding stent has certain limitations. These stents generally have a braided mesh configuration formed by a plurality of helically wound thread elements. This configuration results in a plurality of interstices constituting open spaces between the thread elements. Thus these stents are subject to tissue ingrowth through these interstices. Moreover, these stents may be inadequate if they are to be used to support the flow of fluid or some other media therethrough past a tracheal/esophageal fistula or past an aneurysm in a blood vessel.
A further difficulty with such a self-expanding stent concerns their accurate placement and deployment. Typically an outer tube surrounds the self-expanding stent and radially compresses the stent into a reduced-radius delivery configuration. With the stent positioned at a treatment site, the outer tube is axially withdrawn, permitting the stent to radially self-expand. However, there is friction at the stent/outer tube interface. This friction, at a minimum, makes withdrawal of the tube difficult and, if the friction is too high, could cause the stent to travel with the tube as it is axially withdrawn. As a result, it is difficult precisely to maintain the position of the stent during deployment.
In addition, once the stent is partially deployed, i.e. where the distal portion of the stent is not compressed by the outer tube, friction between the stent and outer tube may prevent the outer tube from being axially moved over the distal portion of the stent to radially compress the stent. Instead, the outer tube may simply push the stent in the distal direction if the outer tube is moved axially distally to reposition the stent by moving the tube back over the stent after partial deployment.
Therefore, it is an object of the present invention to provide a radially self-expanding stent having a barrier region to inhibit tissue ingrowth and to support the flow of fluid or some other media therethrough.
It is a further object of this invention to provide a stent deployment device capable of accurately positioning a radially self-expanding stent near a treatment site and recapturing the stent for repositioning, even if the stent has been partially deployed and is radially expanded over the majority of its axial length.